1. Field of the Invention
The present invention relates to a data communication method of transmitting and receiving data requiring secrecy and data requiring no secrecy, and further relates to a data communication system carrying out such a data communication method.
2. Description of the Related Art
Business transactions are now carried out on open communication networks, such as the Internet, which allow anyone to access it. For such business transactions, data is mainly required, such as data on goods and/or services (hereinafter referred to as "article data" for brevity) to be transmitted by sales companies offering goods and/or services (hereinafter referred to as "articles" for brevity), as well as data transmitted from purchasers buying those articles. Among those data, the article data includes, for example, names, characteristics, functions, prices and so forth of the articles and thus do not require secrecy, or rather, would be preferably delivered to as many people as possible. Therefore, the article data are broadcast to many people from sales companies on the open communication network. On the other hand, the purchaser data includes for example, identities of purchasers, credit card numbers and so forth and thus require secrecy. Thus, the purchaser data are confidentially transmitted to the sales companies from the purchasers concerned on the open communication network. As a typical technique for realizing the confidential communication, encryption of data has been carried out.
On the open communication network, however, even the enciphered data may be subjected to a possibility of surreptitious use by third parties who attempt decryption thereof. Therefore, in the business transactions on the open communication network, it has been difficult to fully avoid leakage to the third parties of the purchaser data which require secrecy.